After watching Shang-Chi and the Legend of the Ten Rings, it's clear that Marvel Studios has big plans for the title character in the MCU moving forward. In the mid-credits scene, we learn that the moment he mastered the Ten Rings, a beacon was activated that has sent a message out to...well, no one seems to know.
Bruce Banner (now in his human form with his arm in a sling) confirms they aren't Vibranium, while Wong reveals that there's no record of the Ten Rings in Kamar-Taj. As for Captain Marvel, she's never seen anything like them during her adventures but doesn't believe they're based on Chitauri tech.
So, who is that beacon calling out to? Initially, the Celestials seem likely, but that doesn't make much sense. Eternals was originally supposed to be released before this movie, and we definitely don't think they're tied to Doctor Strange in the Multiverse of Madness' rumoured big bad (Shuma Gorath).
Instead, we need to take a closer look at the comic books, in which the Ten Rings were actually technology created by an alien race called Makluans. Some of them left their home planet, Kakaranthara, in an effort to conquer other worlds, and they'd eventually land on Earth in ancient China. These space dragons used their powers to shapeshift and blend in, but one of them, Fin Fang Foom, remained in stasis for thousands of years until he was eventually awakened.
We think it's safe to say that these Makluans could be a major threat to the MCU down the line, and seeing as we already know The Great Protector hails from another universe, he could have easily originated on Kakaranthara. With that in mind, something tells us Fin Fang Foom is coming...
...though probably with a new name!